Nanoimprint resist

ABSTRACT

The invention relates to a method for microstructuring electronic components, which yields high resolutions (≦200 nm) at a good aspect ratio while being significantly less expensive than photolithographic methods. The inventive method comprises the following steps: i) a planar unhardened sol film of a nanocomposite composition according to claim  1  is produced; ii) a target substrate consisting of a bottom coat (b) and a support (c) is produced; iii) sol film material obtained in step i) is applied to the bottom coat (b) obtained in step ii) by means of a microstructured transfer embossing stamp; iv) the applied sol film material is hardened; v) the transfer embossing stamp is separated, whereby an embossed microstructure is obtained as a top coat (a). The method for producing a microstructured semiconductor material comprises the following additional steps: vi) the remaining layer of the nanocomposite sol film is plasma etched, preferably with CHF 3 /O 2  plasma; vii) the bottom coat is plasma etched, preferably with O 2  plasma; viii) the semiconductor material is etched or the semiconductor material is doped in the etched areas.

The present invention is in the area of microlithography.

The miniaturization of electronic components, for which a resolutiondown to the range of less than 1 μm is required, has been achievedsubstantially by photolithographic techniques. The limit of resolutionis predetermined by the wavelength of the radiation used for reproducingthe original, so that short-wave radiation, such as high-energy UVradiation, electron beams and X-rays, must be used.

Owing to the occurrence of diffraction effects in the case ofincreasingly small structures, structuring by photolithography reachesits physical limits, which are about 150 nm. On the other hand, theincreasingly high requirements with respect to resolution, wall slopeand aspect ratio (ratio of height to resolution) result in a costexplosion in the case of the apparatuses required for photolithographicstructuring, such as masks, mask aligners and steppers.

In particular, owing to their price of several million US$, modernsteppers are a considerable cost factor in microchip production.

It was therefore the object of the present invention to develop a methodfor the microstructuring of electronic components which gives highresolutions (≦200 nm) in combination with a good aspect ratio but issubstantially more economical than photolithographic methods.

U.S. Pat. No. 5,772,905 describes a nanoimprint method which is based ona thermoplastic deformation of the resist, applied to the whole surfaceof a substrate, by a relief present on a rigid stamp. Thermoplastics(polymethyl methacrylate, PMMA) are used as a resist for hot stamping.Owing to conventional thickness variations of about 100 nm over thetotal wafer surface, it is not possible to structure 6, 8 and 12 inchwafers in one step with a rigid stamp. Thus, a complicated “step andrepeat” method would have to be used, which, however, is unsuitableowing to the reheating of already structured neighboring areas.

WO 99/22 849 discloses a microstructuring method which takes a differentapproach. There, a flexible polydimethylsiloxane stamp having thedesired microstructure is placed on a flat, inorganic substrate. As aresult of the capillary forces, a liquid is subsequently drawn into thestructure. This is an aqueous TEOS solution. The solvent is removed byosmosis and a porous SiO₂ structure remains behind. These layers areused predominantly in biomimetics (composites for teeth and bones).

In U.S. Pat. No. 5,900,160, U.S. Pat. No. 5,925,259 and U.S. Pat. No.5,817,242, a stamp is wet with a UV-curable resist (self-assembledmonolayer, e.g. alkylsiloxane) and then pressed onto a smooth substrate.Analogously to a conventional stamp process, the structured resistmaterial remains when the stamp is raised from the substrate surface.The resist materials used exhibit sufficient wetting with respect to thesubstrate but are not suitable for a lift-off method, nor do they havesufficient etch resistance. The structure dimensions are in the regionof 1 μm and are thus more than 1 order of magnitude too large.

These methods are all unsuitable for achieving the object according tothe invention.

It has been found that the abovementioned requirements can be met by amechanical transfer stamping method if a specific nanocompositecomposition is used as a transfer resist (nanoimprint resist).

The present invention relates to the use of a nanocomposite composition,comprising

-   a) a polymerizable silane of the general formula (I) and/or (II)    and/or condensates derived therefrom    SiX₄  (I)    in which the radicals X are identical or different and are    hydrolyzable groups or hydroxyl group;    R¹ _(a)R² _(b)SiX_((4-a-b))  (II)    in which R¹ is a nonhydrolyzable radical, R² is a radical carrying a    functional group, X has the above meaning and a and b have the value    0, 1, 2 or 3, the sum (a+b) having the value 1, 2 or 3, and-   b) nanoscale particles selected from the group consisting of the    oxides, sulfides, selenides, tellurides, halides, carbides,    arsenides, antimonides, nitrides, phosphides, carbonates,    carboxylates, phosphates, sulfates, silicates., titanates,    zirconates, aluminates, stannates, plumbates and mixed oxides    thereof, as a resist for the microstructuring of semiconductor    materials, flat screens, micromechanical components and sensors.

In the above formulae, the hydrolyzable groups X are, for example,hydrogen or halogen, such as F, Cl, Br or I; alkoxy, preferablyC₁₋₆-alkoxy, such as, for example, methoxy, ethoxy, n-propoxy,isopropoxy and butoxy; aryloxy, preferably C₆₋₁₀-aryloxy, such as, forexample, phenoxy; acyloxy, such as, for example, acetoxy orpropionyloxy; alkylcarbonyl, preferably C₂₋₇-alkylcarbonyl, such as, forexample, acetyl; amino, monoalkylamino or dialkylamino having preferably1 to 12, in particular 1 to 6, carbon atoms in the alkyl group orgroups.

The nonhydrolyzable radical R¹ is, for example, alkyl, preferablyC₁₋₆-alkyl, such as, for example, methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl and tert-butyl, pentyl, hexyl or cyclohexyl; alkenyl,preferably C₂₋₆-alkenyl, such as, for example, vinyl, 1-propenyl,2-propenyl and butenyl; alkynyl, preferably C₂₋₆-alkynyl, such as, forexample, acetylenyl and propargyl; and aryl, preferably C₆₋₁₀-aryl, suchas, for example, phenyl and naphthyl..

Said radicals R¹ and X can, if desired, have one or more conventionalsubstituents, such as, for example, halogen or alkoxy.

Specific examples of the functional groups of the radical R are epoxy,hydroxyl, ether, amino, monoalkylamino, dialkylamino, amido, carboxyl,mercapto, thioether, vinyl, acryloyloxy, methacryloyloxy, cyano,halogen, aldehyde, alkylcarbonyl, sulfo and phosphoric acid groups.These functional groups are preferably bonded to the silicon atom viaalkylene, alkenylene or arylene bridge groups which may be interruptedby oxygen or sulfur atoms or —NH— groups. Said bridge groups arederived, for example, from the abovementioned alkyl, alkenyl or arylradicals. The bridge groups of the radicals R² preferably contain 1 to18, in particular 1 to 8, carbon atoms.

In the general formula (II), a preferably has the value 0, 1 or 2, bpreferably has the value 1 or 2 and the sum (a+b) preferably has thevalue 1 or 2.

Particularly preferred hydrolyzable silanes of the general formula (I)are tetraalkoxysilanes, such as tetraethoxysilane (TEOS) andtetramethoxysilane. Particularly preferred organosilanes of the generalformula (II) are epoxysilanes, such as3-glycidyloxypropyltrimethoxysilane (GPTS) or3-glycidyloxypropyltriethoxysilane, and silanes having reactivepolymerizable double bonds, such as, for example,acryloyloxypropyltrimethoxysilane or3-methacryloyloxypropyltrimethoxysilane. Said silanes or the functionalgroups thereof are preferred because (after hydrolytic polycondensationis complete) they can be used for a polyaddition or polymerizationreaction with, for example, the polymerizable mono- and/or bifunctionalorganic monomers, oligomers and/or polymers and/or react with reactivegroups present on the surface of the nanoscale particles and can thuscontribute to the immobilization (for example by incorporation into anetwork) of the nanoscale particles.

The hydrolysis and polycondensation of the above compounds is carriedout in a conventional manner, if desired in the presence of an acidic orbasic condensation catalyst, such as HCl, HNO₃ or NH₃. Thus, hydrolysisand polycondensation can be effected, for example, under the (generallyknown) conditions of the sol-gel process.

The volume fraction of the nanoscale particles in the nanocompositecomposition is expediently from 1 to 50% by volume, preferably from 1 to30% by volume and in particular from 5 to 20% by volume.

The nanoscale particles usually have a particle size of from 1 to 200nm, preferably from 2 to 50 nm and in particular from 5 to 20 nm.

Nanoscale inorganic particles as such as known, for example from WO96/31572, and are, for example, oxides, such as CaO, ZnO, CdO, SiO₂,TiO₂, ZrO₂, CeO₂, SnO₂, PbO, Al₂O₃, In₂O₃ and La₂O₃; sulfides, such asCdS and ZnS; selenides, such as GaSe, CdSe or ZnSe; tellurides, such asZnTe or CdTe; halides, such as NaCl, KCl, BaCl₂, AgCl, AgBr, Agl, CuCl,CuBr, Cdl₂ or Pbl₂; carbides, such as CeC₂; arsenides, such as AlAs,GaAs or CeAs; antimonides, such as InSb; nitrides, such as BN, AIN,Si₃N₄ or Ti₃N₄; phosphides, such as GaP, InP, Zn₃P₂ or Cd₃P₂;carbonates, such as Na₂CO₃, K₂CO₃, CaCO₃, SrCO₃ and BaCO₃; carboxylates,e.g. acetates, such as CH₃COONa and Pb(CH₃COO)₄; phosphates; sulfates;silicates; titanates; zirconates; aluminates; stannates; plumbates andcorresponding mixed oxides whose composition preferably corresponds tothe composition of conventional glasses having a low coefficient ofthermal expansion, e.g. binary, tertiary or quaternary combinations ofSiO₂, TiO₂, ZrO₂ and Al₂O₃.

Also suitable are, for example, mixed oxides having the perovskitestructure, such as Ba TiO₃ or PbTiO₃. In addition, organically modifiedinorganic particles, such as, for example, particulatepolymethylsiloxanes, methacryloyl-functionalized oxide particles andsalts of methylphosphoric acid may be used.

These nanoscale particles can be produced in a conventional manner, forexample by flame hydrolysis, flame pyrolysis and plasma methodsaccording to the literature mentioned in WO 96/31 572. Stabilizedcolloidal, nanodisperse sols of inorganic particles, such as, forexample, silica sols from BAYER, SnO₂— sols from Goldschmidt, TiO₂ solsfrom MERCK, SiO₂, ZrO₂, Al₂O₃ and Sb₂O₃ sols from Nissan Chemicals orAerosil dispersions from DEGUSSA, are particularly preferred.

The nanoscale particles can be changed in their viscosity behavior bysurface modification.

Suitable surface modifiers, i.e. surface-modifying low molecular weightorganic (=carbon-containing) compounds which have at least onefunctional group which can react and/or (at least) interact with groupspresent on the surface of the powder particles and with the polymermatrix, are in particular compounds having a molecular weight which isnot higher than 500, preferably not higher than 350 and in particularnot higher than 200.

Such compounds are preferably liquid under standard temperature andpressure conditions and preferably have altogether not more than 15, inparticular altogether not more than 10 and particularly preferably notmore than 8 carbon atoms. The functional groups which these compoundsmust carry depend primarily on the surface groups of the nanoscalematerial used in each case and moreover on the desired interaction withthe polymer matrix. Thus, an acid/base reaction according to Bronsted orLewis can take place, for example, between the functional groups of thesurface-modifying compound and the surface groups of the particles(including complex formation and adduct formation). An example ofanother suitable interaction is the dipole-dipole interaction. Examplesof suitable functional groups are carboxyl groups, (primary, secondary,tertiary and quaternary) amino groups and C—H-acidic groups (e.g.β-diketones). A plurality of these groups may also be presentsimultaneously in a molecule (betaines, amino acids, EDTA).

Accordingly, examples of preferred surface modifiers are saturated orunsaturated mono- and polycarboxylic acids (preferably monocarboxylicacids) having 1 to 12 carbon atoms (e.g. formic acid, acetic acid,propionic acid, butyric acid, pentanoic acid, hexanoic acid, acrylicacid, methacrylic acid, crotonic acid, citric acid, adipic acid,succinic acid, glutaric acid, oxalic acid, maleic acid and fumaric acid)and their esters (preferably C₁-C₄-alkyl esters) and amides, e.g. methylmethacrylate.

Examples of further suitable surface modifiers are imides and quaternaryammonium salts of the formula N⁺R¹⁰R²⁰R³⁰R⁴⁰Y⁻ in which R¹⁰ to R⁴⁰ arealiphatic, aromatic or cycloaliphatic groups which may differ from oneanother and which have preferably 1 to 12, in particular 1 to 6, carbonatoms and Y⁻ is an inorganic or organic anion, e.g. Cl or acetate; mono-and polyamines, in particular those of the general formulaR_(3-n)NH_(n), in which n is 0, 1 or 2 and the radicals R, independentlyof one another, are alkyl groups having 1 to 12, in particular 1 to 6and particularly preferably 1 to 4 carbon atoms, e.g. methyl, ethyl,n-propyl, isopropyl and butyl, and ethylenepolyamines, e.g.ethylenediamine, diethylenetriamine; amino acids; imines; β-dicarbonylcompounds having 4 to 12, in particular 5 to 8, carbon atoms, such as,for example, acetylacetone, 2,4-hexanedione, 3,5-heptanedione,acetoacetic acid and C₁-C₄-alkyl acetoacetates; and modified alcoholatesin which some of the OR groups (R as defined above) are substituted byinert organic groups.

For the electrostatic stabilization of the nanoscale particles, forexample, the compounds known for this purpose, such as, for example,NaOH, NH₃, KOH, Al(OH)₃ or tetramethylammonium hydroxide, may also beused.

The nanocomposite compositions used according to the invention mayfurthermore contain polymerizable monofunctional and/or bifunctionalorganic monomers, oligomers and/or polymers from the group consisting of(poly)acrylic acid, (poly)methacrylic acid, (poly)acrylates,(poly)methacrylates, (poly)acrylamides, (poly)methacrylamides,(poly)carbamides, (poly)olefins, (poly)styrene, (poly)amides,(poly)imides, (poly)vinyl compounds, (poly)esters, (poly)arylates,(poly)carbonates, (poly)ethers, (poly)etherketones, (poly)sulfones,(poly)epoxides, fluorine polymers, organo(poly)siloxanes,(poly)siloxanes and hetero(poly)siloxanes.

Examples are (poly)vinyl chloride, (poly)vinyl alcohol,(poly)vinylbutyral, corresponding copolymers, e.g. poly(ethylene-vinylacetate), polyethylene terepthalate, polyoxymethylene, polyethyleneoxide or polyphenylene oxide, organopolysiloxanes or heteropolysiloxanesformed with metals and transition metals, as described, for example, inEP-A-36 648 and EP-A-223 067, and mixtures of two or more of thesepolymers, provided that they are compatible with one another. Instead ofsaid polymers, their oligomers and/or precursors (monomers) may also beused.

Among these polymers, polymers, such as polyacrylates, polymethacrylates(e.g. PMMA), glycidyl ethers, such as, for example, bisphenol Adiglycidyl ether, and polyvinylbutyral, which are soluble in organicsolvents are particularly preferred.

The polymerizable monofunctional and/or bifunctional organic monomers,oligomers and/or polymers may be present in an amount of from 0 to 20mol %, preferably from 0.1 to 15 mol %, in particular from 1 to 10 mol%, based on the polymerizable silane.

A preferred nanocomposite composition furthermore contains afluorosilane of the formula (III)R³(X¹)₃Si  (III)in which

R³ is a partly fluorinated or perfluorinated C₂-C₂₀-alkyl and

X¹ is C₁-C₃-alkoxy, methyl, ethyl or chlorine.

Partly fluorinated alkyl is understood as meaning those alkyl radicalsin which at least one hydrogen atom is replaced by a fluorine atom.

Preferred radicals R³ are CF₃CH₂CH₂, C₂F₅CH₂CH₂, C₄F₉CH₂CH₂,n-C₆F₁₃CH₂CH₂, n-C₈F₁₇CH₂CH₂, n-C₁₀F₂₁CH₂CH₂ and i-C₃F₇O-(CH₂)₃.

Examples of fluorosilanes of the formula (III), which are alsocommercially available, aretridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane, CF₃CH₂CH₂SiCl₂CH₃, CF₃CH₂CH₂ SiCl(CH₃)₂, CF₃CH₂CH₂Si(CH₃)(OCH₃)₂,i-C₃F₇O-(CH₂)₃SiCl₂CH₃, n-C₆F₁₃CH₂CH₂SiCl₂CH₃ and n-C₆F₁₃CH₂CH₂SiCl(CH₃)₂.

The fluorosilanes of the formula (III) may be present in an amount offrom 0 to 3% by weight, preferably from 0.05 to 3% by weight,particularly preferably from 0.1 to 2.5% by weight, in particular from0.2 to 2% by weight, based on the total weight of the nanocompositecomposition. The presence of fluorosilanes is required in particularwhen a glass or silica glass stamp is used as the transfer imprintstamp.

The nanocomposite composition expediently contains a polymerization,polyaddition and/or polycondensation catalyst which can thermally and/orphotochemically induce crosslinking and curing (referred to collectivelyas “crosslinking initiator”).

Photoinitiators used may be, for example, the commercially availableinitiators. Examples of these are Irgacure® 184 (1-hydroxycyclohexylphenyl ketone), Irgacure® 500 (1-hydroxycyclohexyl phenyl ketone,benzophenone) and other photoinitiators of the Irgacure® type availablefrom Ciba; Darocur® 1173, 1116, 1398, 1174 and 1020 (available fromMerck), benzophenone, 2-chlorothioxanthone, 2-methylthioxanthone,2-isopropylthioxanthone, benzoin, 4,4′-dimethoxybenzoin, benzoin ethylether, benzoin isopropyl ether, benzil dimethyl ketal,1,1,1-trichloroacetophenone, diethoxyacetophenone and dibenzosuberone.

Suitable thermal initiators are, inter alia, organic peroxides in theform of diacyl peroxides, peroxydicarbonates, alkyl peresters, dialkylperoxides, perketals, ketone peroxides and alkyl hydroperoxides.Specific examples of such thermal initiators are dibenzoyl peroxide,tert-butyl perbenzoate and azobisisobutyronitrile.

When used, the crosslinking initiator is usually employed in an amountof from 0.1 to 5, preferably from 0.5 to 3, % by weight, based on thenanocomposite composition.

The invention furthermore relates to a microlithographic arrangementcomprising

-   -   a) a microstructured layer of a nanocomposite composition as a        top coat;    -   b) a bottom coat comprising an aromatics-containing (co)polymer        containing novolaks, styrenes, (poly)hydroxystyrenes and/or        (meth)acrylates;    -   c) a substrate.

The substrate is preferably a semiconductor material to be structured,e.g. a silicon wafer or indium tin oxide layers on glass.

The bottom coat present thereon should have good adhesion both to thetop coat a) and to the substrate and preferably has a layer thickness offrom about 0.1 to 20 μm.

The invention furthermore relates to a method for the production of sucha microlithographic arrangement, comprising the steps:

-   -   i) production of an uncured sol film of the nanocomposite        composition described above;    -   ii) production of a target substrate comprising bottom coat b)        and substrate c);    -   iii) transfer of sol film material from i) by means of a        microstructured transfer imprint stamp to the bottom coat b) in        ii);    -   iv) curing of the transferred sol film material;    -   v) removal of the transfer imprint stamp to give an imprinted        microstructure as top coat a).

The uncured sol film i) is expediently applied to a planar arrangement,comprising a support, e.g. glass, silica glass, plastic or siliconwafer, and/or an adhesion-promoting film. The adhesion-promoting filmcontains organic polymers which ensure good wetting with respect to thesupport and the nanocomposite sol film to be deposited thereon. Theadhesion-promoting film may comprise, for example, anaromatics-containing polymer or copolymer, containing novolaks,styrenes, (poly)hydroxystyrenes and/or (meth)acrylates. Theadhesion-promoting film can be applied to the support by known methods,such as, for example, spin coating.

The nanocomposite composition according to the invention is then appliedas a sol film to the adhesion-promoting film, expediently in a filmthickness of from 0.5 to 1 μm, by known methods, such as, for example,spin coating, spray coating or roller coating. The sol film preferablyhas a viscosity of from 80 mPa s to 2 Pa s, preferably from 100 mPa s to1 Pa s and particularly preferably from 200 mPa s to 600 mPa s.

The nanocomposite composition can be applied either as such orpreferably as a solution in an organic solvent. Examples of suitablesolvents are alcohols, such as butanol, ketones, such as acetone,esters, such as ethyl acetate, ethers, such as tetrahydrofuran, andaliphatic, aromatic and halogenated hydrocarbons, such as hexane,benzene, toluene and chloroform.

The nanocomposite composition can be prepared, for example, bydispersing the nanoscale particles in one of the abovementioned solventsand/or one of said polymerizable compounds, for example with stirring orby means of ultrasonics. The dispersion obtained is then mixed with theother components of the nanocomposite composition, if required withdilution with a solvent. The solvent used for dilution is eitheridentical to the solvent used for the dispersion or miscible therewith.

If the solvent used does not evaporate during the application of thenanocomposite sol film, it is expedient substantially to remove thesolvent after application of the film by suitable measures, such as, forexample, heating, since otherwise transfer of the sol film material bymeans of a transfer imprint stamp is problematic.

The target substrate can be produced by the same methods. The bottomcoat can have a composition which is the same as or similar to that ofthe above-described adhesion-promoting film of the starting substrate.

After application of the nanocomposite sol and evaporation of thesolvent in air, the fluorosilane molecules have accumulated at thesurface, into which the glass or silica glass transfer imprint stamp isthen pressed for from about 5 to 300 seconds, preferably from 10 to 60seconds (immersion time).

The transfer imprint stamp may also consist of silicone rubber. In thiscase, no fluorosilanes of the formula (III) are required.

The fluorinated side chains of the fluorosilane molecules are inprinciple repelled by the hydrophilic surface of the glass or silicaglass stamp and only weakly attracted by the surface of theadhesion-promoting film or of the substrate, and therefore diffuse in aconcentration gradient. After said immersion time, the transfer imprintstamp is pulled out of the excess nanocomposite sol film. The adhesionof the sol film material in the 30 to 500 nm, preferably 100 to 200 nm,deep and broad microchannels of the stamp due to capillary forces anddue to partial removal of the fluorosilane molecules from the (silica)glass surface is sufficiently great for it to be picked up by the stamp.If the immersion time is not reached, the transfer is incomplete. Thetransfer of the microstructure to the target substrate is effected bythe air, preferably in the course of from 10 to 300 seconds. Thefluorosilane accumulates at the interface with the air, so that thewetting of the stamp is very good and the sol does not contract to adrop in the transfer stamp.

After the transfer stamp is placed on the bottom coat b) of the targetsubstrate, the stamp is pressed against the bottom coat b) for aduration of from 10 to expediently 300 seconds, preferably from 20 to 50seconds, in particular from 30 to 40 seconds, under a pressure of from10 to 100 kPa. During this, the fluorosilane diffuses back in thedirection of the (silica) glass surface, so that, after curing, theadhesion to the bottom coat is sufficiently good and that to thetransfer stamp is sufficiently poor. The layer thickness of thetransferred material is from 50 to 1 000 nm, preferably from 150 to 500nm.

If the same nanocomposite sol were to be used without fluorosilane andtransferred by means of a silica glass stamp, no structure would bedeposited on the target substrate. The sol remains completely in thestamp.

While the transfer imprint stamp rests on the bottom coat, thermalcuring or UV curing takes place. In the case of UV-transparent transferstamps, curing by UV radiation is preferred. After heating to about 80to 150° C. for from about 1 to 10 minutes and/or UV irradiation for fromabout 5 to 20 minutes, the transferred sol film material has cured andthe transfer imprint stamp is removed to give an imprintedmicrostructure (top coat a).

An investigation of this microstructured arrangement with the aid of ascanning electron microscope shows that not only the imprintedmicrostructure remains behind on the target substrate but also anunstructured residual layer of the nanocomposite sol film having athickness of less than 30 nm.

For subsequent use in microelectronics, it is necessary for thenanocomposite sol film and the bottom coat to have different etchresistance in order to achieve a steep wall slope and a high aspectratio (ratio of height of the lands to distance between two lands).

Thus, the nanocomposite composition used according to the invention canbe etched with a CHF₃/O₂ gas mixture but not by an oxygen plasma. In thecase of the bottom coat, the opposite is true.

The present invention therefore also relates to a method for theproduction of a microstructured semiconductor material, comprising theabovementioned steps i) to

-   -   v), support c) being the semiconductor material to be        structured, and the steps    -   vi) plasma etching of the residual layer of the nanocomposite        sol film, preferably with CHF₃/O₂ plasma,    -   vii) plasma etching of the bottom coat, preferably with O₂        plasma,    -   viii) doping of the semiconductor material in the etched areas,        or etching of the semiconductor material.

After the etching process, the resist coating can be removed by means ofconventional solvents, such as, for example, tetramethylammoniumhydroxide.

Scanning electron micrographs show that, after the method according tothe invention, nanostructures having an edge length of about 150 nm anda wall slope of about 90° are imprinted.

EXAMPLES

1) Preparation of a Nanocomposite Composition

236.1 g (1 mol) of glycidyloxypropyltrimethoxysilane (GPTS) are refluxedwith 27 g (1.5 mol) of water for 24 hours. Methanol formed is thenstripped off on a rotary evaporator at 70° C.

345 g of tetrahexylammonium hydroxide-modified silica sol (SiO₂ colloid,diameter about 10 nm, about 30% strength by weight in isopropanol,modified with 2.4 mg of tetrahexylammonium hydroxide solution (40%strength by weight in water) per g of silica sol) are added, withstirring, to the GPTS condensate thus prepared. The isopropanol is thenremoved in a rotary evaporator. In each case 1% by weight, based on thesol, of a cationic photoinitiator (UVI 6974, Union Carbide) andtridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane, and 22.3 g(0.0714 mol) of bisphenol A diglycidyl ether, are added to thesolvent-free sol.

The sol is diluted by adding isopropoxyethanol until a nanocompositecomposition having a viscosity of about 300 mPa s is obtained.

2) Preparation of the Novolak for Starting Substrate and TargetSubstrate:

120 g of m-cresol, 60 g of p-cresol and 106.8 g of 37% strength byweight formalin are heated together with 4 g of oxalic acid dihydratefor 6 hours at 100° C. For the removal of water and unconverted cresol,formaldehyde and oxalic acid by distillation, the reaction mixture isheated to 200° C. and the pressure is reduced to 50 mbar. 172 g ofnovolak are obtained as a solid.

3) Production of the Starting Substrate:

a) A 4 inch silicon wafer pretreated with hexamethyidisilazane is coatedin a spin coater with a novolak solution (17.5 g of the novolak preparedabove in 82.3 g of PGMEA). A softbake is then effected for 90 s at 110°C. and a hardbake for 90 s at 235° C., so that the resulting layerthickness is about 500 nm (adhesion-promoting layer).

b) The nanocomposite composition prepared above is applied by spincoating (2 000 revolutions, 30 s) to the adhesion-promoting layer thusprepared. For removal of the solvent, the sol film is dried for 1 minuteat about 25° C. without the sol film curing.

The layer thickness of the nanocomposite sol film is about 500 nm.

4) Production of the Target Substrate:

The target substrate is produced analogously to 3 a).

5) Transfer and Imprinting of the Microstructure onto the TargetSubstrate:

The imprinting apparatus is a computer-controlled test machine (Zwick1446 model) which makes it possible to program loading and relief speedsand to maintain defined pressures over a specific time. The forcetransmission is effected via a shaft to which the imprinting stamp isfastened by means of a joint. This permits the exact orientation of theimprint structure relative to the substrate. A metal halide lamp(UV-S400 model from Panacol-Elosol GmbH, UV-A radiation 325-380 nm)serves for the photochemically initiated curing.

A microstructured silica glass stamp (4×4 cm, structure depth 200 nm) ispressed under a force of 40 N into the uncured sol film of the startingsubstrate produced above. After a waiting time of 15 s, the stamp ispulled out of the excess sol film. The stamp now completely wet with solfilm material is held in the air for 30 s, then placed on the targetsubstrate produced above and pressed for 35 s with a force of 50 N ontothe bottom coat, the transferred film being cured by the UV lamp. Afteran imprinting and exposure time of 5 minutes altogether, the stamp isremoved and the cured microstructured sol film material is retained onthe target substrate. A scanning electron micrograph of the coatingshows that structures having a geometry of 150 nm×150 nm with a steepwall slope are reproduced. A residual layer thickness of 25 mm of solfilm material is present between bottom coat and the transferredstructures.

6) Etching Process

The substrate was etched under the following conditions:

1) with CHF₃/O₂ (25:10), 300 W, 50 mmHg, RIE mode, anisotropic; forremoval of the residual top coat;

2) with O₂, 300 W, 50 mmHg, RIE mode, anisotropic; for removal of thebottom coat.

Aspect ratio about 3.

1. A microlithographic arrangement comprising a) a microstructured layerof a nanocomposite composition comprising a1) a polymerizable silane ofthe general formula (I) and/or (II) and/or condensates derived therefromSiX₄  (I) in which the radicals X are identical or different and arehydrolyzable groups or hydroxyl groups;R¹ _(a)R² _(b)SiX_((4-a-b))  (II) in which R¹ is a nonhydrolyzableradical, R² is a radical carrying a functional group, X has the abovemeaning and a and b have the value 0, 1, 2 or 3, the sum (a+b) havingthe value 1, 2 or 3, and a2) nanoscale particles selected from the groupconsisting of the oxides, sulfides, selenides, tellurides, halides,carbides, arsenides, antimonides, nitrides, phosphides, carbonates,carboxylates, phosphates, sulfates, silicates, titanates, zirconates,aluminates, stannates, plumbates and mixed oxides thereof, as a topcoat; b) a bottom coat comprising an aromatics-containing polymer orcopolymer containing novolaks, styrenes, (poly)hydroxystyrenes and/or(meth)acrylates; c) a substrate.
 2. The microlithographic arrangement asclaimed in claim 1, wherein the top coat a) is a sol film.
 3. Themicrolithographic arrangement as claimed in claim 1 wherein thesubstrate c) is a semiconductor material.
 4. The microlithographicarrangement as claimed in claim 1, wherein the nanocomposite compositioncontains from 1 to 50 percent by volume, preferably from 1 to 30 percentby volume, of nanoparticles.
 5. The microlithographic arrangement asclaimed in claim 1, where the nanoscale particles have beensurface-modified with compounds selected from the group consisting ofthe carboxylic acids, carboxamides, carboxylic esters, amino acids,β-diketones, imides, quaternary ammonium salts of the general formulaN⁺R¹⁰R²⁰R³R⁴⁰Y⁻, where the radicals R¹⁰ to R⁴⁰ are identical ordifferent and may be aliphatic, aromatic and/or cycloaliphatic groupsand Y⁻ is an inorganic or organic anion.
 6. The microlithographicarrangement as claimed in claim 1, wherein the nanocomposite compositioncontains polymerizable monofunctional and/or bifunctional monomers,oligomers and/or polymers selected from the group consisting of(poly)acrylic acid, (poly)methacrylic acid, (poly)acrylates,(poly)methacrylates, (poly)acrylamides, (poly)methacrylamides,(poly)carbamides, (poly)olefins, (poly)styrene, (poly)amides,(poly)imides, (poly)vinyl compounds, (poly)esters, (poly)arylates,(poly)carbonates, (poly)ethers, (poly)etherketones, (poly)sulfones,(poly)epoxides, fluorine polymers, organo(poly)siloxanes,(poly)siloxanes and hetero(poly)siloxanes.
 7. The microlithographicarrangement as claimed in claim 1, where the nanocomposite compositioncontains a fluorosilane of the formula (III)R³(X¹)₃Si  (III) in which R³ is a partly fluorinated or perfluorinatedC₂-C₂₀-alkyl and X¹ is C₁-C₃-alkoxy, chlorine, methyl or ethyl.
 8. Themicrolithographic arrangement as claimed in 1, wherein the nanocompositecomposition contains a crosslinking initiator.
 9. A method for theproduction for microlithographic arrangement as claimed in claim 1,comprising the steps: i) production of a planar uncured sol film of saidnanocomposite; ii) production of a target substrate comprising a bottomcoat b) and a support c); iii) transfer of sol film material from i) bymeans of a microstructured transfer imprint stamp to the bottom coat b)in ii); iv) curing of the transferred sol film material; v) removal ofthe transfer imprint stamp to give an imprinted microstructure as topcoat a).
 10. The method as claimed in claim 9, wherein the uncured solfilm i) is applied to a planar starting substrate comprising a supportand/or an adhesion-promoting film.
 11. The method as claimed in claim 9,wherein the transfer imprint stamp comprises silicone, glass or silicaglass.
 12. The method as claimed in claim 9 wherein the transfer imprintstamp is pressed into the sol film i) for from 5 to 300 seconds, thenremoved and placed on the bottom coat b) in the course of from 10 to 300seconds and pressed against b) for a time of from 10 to 300 secondsunder a pressure of from 10 to 100 kPa.
 13. The method as claimed inclaim 9 wherein thermal curing or UV curing is carried out while thetransfer imprint stamp is pressed against b).
 14. A method for theproduction of a microstructured semiconductor material, comprising thesteps i) to v) as claimed in claim 9, support c) being the semiconductormaterial to be structured, and the steps vi) plasma etching of theresidual layer of the nanocomposite sol film, preferably with CHF₃/O₂plasma, vii) plasma etching of the bottom coat, preferably with O₂plasma, viii) etching of the semiconductor material or doping of thesemiconductor material in the etched areas.